Remove #pragma once. Just from base/ for now.

base/threading/simple_thread.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // WARNING: You should probably be using Thread (thread.h) instead.  Thread is
 //          Chrome's message-loop based Thread abstraction, and if you are a
 //          thread running in the browser, there will likely be assumptions
 //          that your thread will have an associated message loop.
 //
 // This is a simple thread interface that backs to a native operating system
@@ skipping 21 matching lines @@
 //   thread.Start();
 //   // Start will return after the Thread has been successfully started and
 //   // initialized.  The newly created thread will invoke runner->Run(), and
 //   // run until it returns.
 //   thread.Join();  // Wait until the thread has exited.  You *MUST* Join!
 //   // The SimpleThread object is still valid, however you may not call Join
 //   // or Start again.
 
 #ifndef BASE_THREADING_SIMPLE_THREAD_H_
 #define BASE_THREADING_SIMPLE_THREAD_H_
-#pragma once
 
 #include <string>
 #include <queue>
 #include <vector>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/threading/platform_thread.h"
 #include "base/synchronization/lock.h"
@@ skipping 129 matching lines @@
   int num_threads_;
   std::vector<DelegateSimpleThread*> threads_;
   std::queue<Delegate*> delegates_;
   base::Lock lock_;            // Locks delegates_
   WaitableEvent dry_;    // Not signaled when there is no work to do.
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_SIMPLE_THREAD_H_